Electric shock is the physiological reaction or injury caused by electric current passing through the (human) body. Typically, the expression is used to describe an injurious exposure to electricity. It occurs upon contact of a (human) body part with any source of electricity that causes a sufficient current through the skin, muscles, or hair. Very small currents can be imperceptible. Larger current passing through the body may make it impossible for a shock victim to let go of an energized object. Still larger currents can cause fibrillation of the heart and damage to tissues. Death caused by an electric shock is called electrocution. An electrical injury has many consequences to a body as the electrical currents can travel through the nervous system and burn out tissue in patches along the way. This can leave bizarre symptoms anywhere on the body and may lead to complex regional pain syndrome. Wiring or other metalwork which is at a hazardous voltage which can constitute a risk of electric shock is called "live", as in "live wire". Shocks can be caused by direct or indirect contact. Contact with an exposed conductive part under fault conditions is called indirect contact. IEC requires certain degrees of ingress protection against direct contact. Indirect contact protections can be achieved by earthed equipotential bonding and automatic disconnection of supply by using fuses for example.